Siphon
At the end of this unit'sUnitUnits fall under 2 categories: party and enemy. These 2 categories, in relation to one another, are referred to as opposing units. turnTurnDuring a battle round, each unit on the battle map takes a turn. Some abilities are limited to a certain number of uses per turn; that limit is reset at the start of each unit's turn., remove 1 HP from each non-quest unitQuest UnitQuest units (white chips, brown border) are not mixed into draw bags at setup or after battles. Quest units cannot gain status effects from abilities or rules unless explicitly stated. within rangeRangeRange (or distance) from one hex to another is measured by counting the number of hexes between those hexes, including the destination hex, regardless of whether those hexes are occupied.. Place all HP removed under this unit's chip (may exceed HealthHealthHP chips are stacked underneath an adventurer's chip and removed to indicate how much damage they have taken relative to their Health stat. stat).
Is Siphon considering taking damage?
"Remove 1 HP" is not considered taking damage.
Does Siphon effect units that are untargetable (e.g. Stealth)?
Untargetable units are still effected. Siphon is not a targeting skill and Stealth just prevents you from being targeted, not from being affected by any skill.
SourceWill a unit with Siphon remove it's last HP and defeat itself?
Siphon affects each other non-quest unit in range. It's not meant to defeat itself at 1 HP.
Source